1. Field of the Invention
The present invention relates to a power generation control device, and more particularly to a power generation control device for controlling power generation so that an output current generated from an engine driven generator can be supplied to a battery and a load in only a predetermined region of the engine strokes where a friction in the engine is low.
2. Background of the Invention
In a vehicle adapted to be driven by an engine, such as a motorcycle and a four-wheel vehicle, a generator adapted to be driven by the engine is provided. A battery for supplying electric power to be used in the vehicle is charged with an output current generated from the generator. Further, in general, an on-vehicle generator selves also as an engine starting motor.
It is known that the amount of the power generation period by an on-vehicle generator is variably controlled according to the load on an engine in the vehicle. For example, JP-A-H3-504407 discloses an AC generator type battery charging method such that a power generation function is stopped when a battery voltage reaches a predetermined level; when a heavy load is applied to an engine, the power generation function of the AC generator is stopped or reduced in spite of the fact that the charged condition of the battery is lower than the predetermined level, thereby preventing a reduction in efficiency of the engine.
Further, Japanese Patent Laid-open No. Hei 3-212200 discloses a device for controlling a field winding current according to an electrical load condition or an operational condition of an automobile, wherein when knocking occurs, the field current in a generator is controlled or stopped.
In the existing power generation control device or charge control device as described in JP-A-H3-504407 and Japanese Patent Laid-open No. Hei 3-212200, the amount of power generation period can be limited when the load on the engine is large, thereby suppressing an increase in engine load. In a four-stroke cycle engine, a friction (a force acting in a direction opposite to the direction of movement of a piston during the operation of the engine from the viewpoint of engine function) differs according to the engine stroke. Accordingly, in the case that the amount of power generation period is controlled only based on the loaded condition of the engine without considering this friction, it is difficult to reduce torque fluctuation due to the friction difference between the strokes.
Particularly in the case that the engine is operated in a low engine speed region, the output torque of the engine is generally low. Accordingly, even though the amount of power generation period is limited, there is a possibility that the engine operation may become unstable due to the torque fluctuation caused by the friction difference between the strokes. In other words, even though the amount of power generation period is controlled according to only the loaded condition of the engine in general, the smoothness of the engine operation cannot be significantly improved.